Endodontic file combining active and passive cutting edges
An endodontic reamer/file for cleaning/shaping a tooth root canal having an elongated shank with a proximal end portion, a distal end and a tapered working portion having a longitudinal axis, the external surface of the shank working portion being defined by a plurality of at least two equally spaced apart continuous concaved helical flutes providing concave flute surfaces, the flute surfaces having therebetween an equal number of spiraled, spaced apart flanges, each flange having in a plane perpendicular the longitudinal axis a single outer end surface having opposed first and second ends, each first end forming an active spiraled leading scraping/cutting edge and each second end forming a passive spiraled edge.
1. An endodontic instrument comprising at least a first and a second transverse sections, each of different cross-sectional area and different shape than the other and located along a length of a tapered working portion of the endodontic instrument, the first transverse section being located nearer a tip end of endodontic instrument than the second transverse section, the first and second transverse sections each including at least three arcuate-shaped flute surfaces, the at least three arcuate-shaped flute surfaces of the first and second transverse sections forming a central core portion of the tapered working portion of the endodontic instrument;
wherein each arcuate-shaped flute surface intersecting with an adjacent flange end surface, forming a single cutting edge which is an active cutting edge having a positive rake angle when the endodontic instrument is rotated in one direction and a passive cutting edge having a negative rake angle when the instrument is rotated in an opposite direction, wherein the different shapes of the first and second transverse sections being defined in part by an angle of the flange end surface of each transverse section, the angle of the flange end surface being between the flange end surface and a radius drawn from a rotational axis of the endodontic instrument at an angle of 90 degree; and
wherein each arcuate-shaped flute surface being defined by a radius R, the radius R selected to provide a concave-shaped flute surface, the radius R of the at least three arcuate-shaped flute surfaces of the first transverse section being a shorter radius than that of the at least three arcuate-shaped flute surfaces of the second transverse section, the radius R and the angle of the flange end surface of each transverse section being selected to define the positive rake angle, the positive rake angle of the first transverse section being a different rake angle than the positive rake angle of the second transverse section.